To sign in to Messenger on a Mobile Device:

1. Type in  your Yahoo! ID and password as a new text message on your mobile device, seperated by one space. For example: Yahoo!ID Password
2. Send this message to the short code for your wireless carrier. Wireless carrier short codes can be found here.
3. You should now receive two messages from Yahoo!.

• The first confirms that you're signed into the service.
• The second message lists your online friends.

If your sign in is not successful, you'll receive a message stating "Invalid Yahoo! ID or password. Please try again."

To sign out of Messenger:

1. Type the word out as a new text message on your mobile device.
2. Send this message to the short code for your wireless carrier. Wireless carrier short codes are listed here.
3. You're now signed out. You'll receive a confirmation message acknowledging your sign out request. Any offline messages will be archived and retrieved the next time you log in to Yahoo! Messenger on your computer.

Note: You may incur charges for sending and receiving text messages on your mobile phone. Please see your carrier service agreement for more information.

Mobile